The invention relates generally to semiconductor devices and fabrication methods, and, more particularly, to an ONO interpoly dielectric for flash memory cells and method for fabricating the same using a single wafer low temperature deposition process.
One type of semiconductor device is a flash memory device, which includes a floating-gate electrode for storing electrical charge. The electrical charge is provided from a channel region underneath the floating-gate electrode. The floating-gate electrode typically includes a dielectric material for storing the electrical charge. A common dielectric structure for a floating-gate electrode is an oxide-nitride-oxide nitride-oxide (xe2x80x9cONOxe2x80x9d) structure.
This type of structure plays an essential role regarding operating characteristics and reliability of the flash memory device. A high quality ONO dielectric structure should provide, e.g., low defect density, long mean time to failure, and high charge retention capability.
One method for forming an ONO dielectric uses a single wafer thermal process. A conventional process requires an elevated high temperature of about 800xc2x0 C. to deposit the dielectric film. This process has a number of disadvantages because of the high temperature. For example, the high temperature process can cause surface roughness of the dielectric material, low time dependent dielectric breakdown (xe2x80x9cTDDBxe2x80x9d), and low yields.
Thus, what is needed is a low temperature deposition process to deposit an ONO dielectric material and to reduce the surface roughness of the ONO dielectric material.
In accordance with the invention, there is provided a method of manufacturing a semiconductor device, including providing a wafer substrate, forming a first silicon oxide layer over the wafer substrate, forming a nitride layer over the first silicon oxide layer using a low temperature deposition process, and forming a second silicon oxide layer over the nitride layer. In one aspect, the first silicon oxide layer is formed over a floating gate poly.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.